State-of-the-art MEMS vibratory gyroscopes typically use metal electrodes placed directly in contact with the mechanical resonator structure or the resonant structure itself is fabricated from conducting or semiconducting materials. When metal electrodes are used, the high mechanical quality factor (Q) of the resonator is spoiled and fabrication tolerance of the metal contacts reduces the symmetry of the resonator. Both reduction in Q and symmetry reduce the gyroscope sensitivity and increase bias drift, sometimes by orders of magnitude. When conducting or semiconducting materials are used, such as Si, Ni, and so on, the gyroscope either suffers from mechanical loss of the material or inherent asymmetry due to asymmetry of crystalline materials.
Several experimental groups have recently realized that an electric gradient force can be used to effectively drive nano-mechanical devices. Unterreithmeier, Q. P., Weig, E. M., & Kotthaus, J. P. in “Universal transduction scheme for nanomechanical systems based on dielectric forces” Nature, Vol 458, pp: 1001-1003, 2009 describe that an electric gradient force may be used to drive cantilevers. Kwan H. Lee, T. G. in “Cooling and control of a cavity optoelectromechanical system” Phys. Rev. Lett., Vol 104, 123604 2010 describe how an electric gradient force may be used to control a cavity. The physical description of the electric gradient force and method for calculating it is found in standard physics textbooks, such as Griffiths, D. J. (1999). Introduction to Electrodynamics. Saddle River: Prentice Hall.
While this prior art has focused on nano-mechanical structures, electric gradient forces have not been applied to larger micro scale inertial sensors.
What is needed is a MEMS gyroscope with tactical and navigation grade performance. Also needed are MEMS gyroscopes that are low cost and have a small size and low power and weight. The embodiments of the present disclosure answer these and other needs.